In an MRI scan, a higher magnetic field requires higher frequency radio waves to resonate with the nuclear type whose density and location is being imaged. What effect does going to a larger magnetic field have on the most efficient antenna to broadcast those radio waves? Does it favor a smaller or larger antenna?

Laser vision correction often uses an excimer laser that produces 193-nm electromagnetic radiation. This wavelength is extremely strongly absorbed by the cornea and ablates it in a manner that reshapes the cornea to correct vision defects. Explain how the strong absorption helps concentrate the energy in a thin layer and thus give greater accuracy in shaping the cornea. Also explain how this strong absorption limits damage to the lens and retina of the eye.

Problems&Exercises

(a) Two microwave frequencies are authorized for use in microwave ovens: 900 and 2560 MHz. Calculate the wavelength of each. (b) Which frequency would produce smaller hot spots in foods due to interference effects?

(a) 33.3 cm (900 MHz) 11.7 cm (2560 MHz)

(b) The microwave oven with the smaller wavelength would produce smaller hot spots in foods, corresponding to the one with the frequency 2560 MHz.

A radar used to detect the presence of aircraft receives a pulse that has reflected off an object
6×10−5ssize 12{6´"10" rSup { size 8{-5} } " s"} {} after it was transmitted. What is the distance from the radar station to the reflecting object?

If you wish to detect details of the size of atoms (about
1×10−10msize 12{1´"10" rSup { size 8{-"10"} } " m"} {} ) with electromagnetic radiation, it must have a wavelength of about this size. (a) What is its frequency? (b) What type of electromagnetic radiation might this be?

If the Sun suddenly turned off, we would not know it until its light stopped coming. How long would that be, given that the Sun is
1.50×1011msize 12{1 "." "50"´"10" rSup { size 8{"11"} } " m"} {} away?

Distances in space are often quoted in units of light years, the distance light travels in one year. (a) How many meters is a light year? (b) How many meters is it to Andromeda, the nearest large galaxy, given that it is
2.00×106size 12{2 "." "00"´"10" rSup { size 8{6} } } {} light years away? (c) The most distant galaxy yet discovered is
12.0×109size 12{"12" "." 0´"10" rSup { size 8{9} } } {} light years away. How far is this in meters?

A quantity that has both a magnitude AND a direction. E.g velocity, acceleration, force are all vector quantities. Hope this helps :)

deage

what is the difference between velocity and relative velocity?

Mackson

Velocity is the rate of change of displacement with time. Relative velocity on the other hand is the velocity observed by an observer with respect to a reference point.

Chuks

what do u understand by Ultraviolet catastrophe?

Rufai

A certain freely falling object, released from rest, requires 1.5seconds to travel the last 30metres before it hits the ground. (a) Find the velocity of the object when it is 30metres above the ground.

Any object in motion will come to rest after a time duration. Different objects may cover equal distance in different time duration. Therefore, motion is defined as a change in position depending on time.

Chuks

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